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| Home > Publications database > Phasensynchronisation von Hochtemperatur-Josephson-Kontakten mit Parallelwiderständen unter Mikrowelleneinstrahlung |
| Home > Publications database > Phasensynchronisation von Hochtemperatur-Josephson-Kontakten mit Parallelwiderständen unter Mikrowelleneinstrahlung |
| Book/Report | FZJ-2020-00405 |
2000
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/23961
Report No.: Juel-3769
Abstract: In recent years, microwave integrated circuits of low temperature superconducor (LTS) thin films have been used for the metrological representation of the Volt as voltage standards. The core element of these circuits is a series array of some thousand Josephson Tunnel-junctions. To obtain the metrological state, all junctions have to be synchronized with an external microwave signal. A disadvantage of the junction type in use is their hysteretic behaviour. It prevents the rapid setting of different output voltages (programmable voltage standards). The use of nonhysteretic junctions can overcome this drawback and is an aim of todays metrological research. In this work, high temperature superconductor (HTS) Josephson junctions have been investigated concerning their possible use in metrological arrays, because of their nonhysteretic behaviour and the possible operation at elevated temperatures. However, the requirements on parameter spreads are very tight and difficult to achieve with HTS technology at time. Therefore, a special type of HTS junctions, shunted YBCO bicrystal junctions, has been focused on. It is demonstrated, that shunting the junctions with an in-situ metal cap layer is an effective way to suppress the spread in normal resistance and to meet the metrological requirement. Measurements and simulations of the shunted bicrystal junctions prove their conformity to the RSJ-model and their capacity to generate large Shapirostep amplitudes of more than 1 mA at temperatures above T = 77 K, which provides the metrological steepness of the steps in spite of thermal noise. Based on these results, the synchronisation in series arrays of several hundred bicrystal junctions has been investigated. Arrays with three different types of microwave power coupling have been designed, fabricated and characterized. Within the first type, power is irradiated from a waveguide onto the array. The second type is a more complex design with the junctions being included in a coplanar waveguide. The third type represents anew integrated concept with inductive power coupling. Synchronization of more than hundred junctions has been obtained, providing output voltages of several mV. The measurements show, that inhomogeneous power distribution along the arrays limits theamount of synchronized junctions. A new concept for a programmable HTS voltage standard with larger tolerance towards geneous microwave distribution is reported. In conclusion, this work demonstrates the high potential of shunted YBCO bicrystal junctions for metrological applications. For the first time, synchronization of HTS junctions in series arrays has been used to generate voltages in the mV regime with metrological accuracy.
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